Appropriate psychological services and career counseling for minorities depend upon accurate psychological assessment. Transporting psychological tests developed for one cultural group to another may result in inaccurate assessment. Accurate assessment presupposes testing individuals in their preferred language. The potential for inaccurate assessment, however, is not eliminated when a test is translated into another language. Unless it is determined that test items measure in an equivalent fashion for both cultures, it is not certain whether group differences are real or are the product of measurement artifacts. Statistical methods based on item response theory (IRT) permit the identification of items that lack measurement equivalence, in other words, items that display differential item functioning (DIF). IRT-based methods will be used to examine the measurement equivalence of psychological and career counseling tests for Mexican Americans. DIF will be examined for English and Spanish versions of the following tests: the Minnesota Multiphasic personality Inventory- 2 (MMPI-2), the Strong Interest Inventory (SII), and the Campbell Interest and Skills Survey (CISS). These tests will be administered to subjects in their dominant language. The three subject groups used in the DIF analyses include: 500 Anglos, 500 English-speaking Hispanics, and 500 Spanish-speaking Hispanics. Three comparisons will be made: Anglos versus English-speaking hispanics, Anglos versus Spanish-speaking hispanics, and English-speaking Hispanics versus Spanish-speaking Hispanics. Results of this study will; (1) establish the measurement equivalence of the tests in question, and (2) compare the practical application of two methods for detecting DIF.